The purpose of this engineering study is to develop preliminary design and cost data ( -30%) pertinent to construction and operation of a 500 barrels per day, demonstration-scale oil shale retorting complex utilizing Allis-Chalmers'patented roller grate retort technology. Of primary concern is the minimizing of overall project costs without sacrificing goals det for the planned demonstration facility. These goals are defined as follows: demonstrate the ability and reliability of the roller grate device to process oil shale on a continuous basis; demonstrate the capability of the retorting process configuration to safely, economically, and reliably produce shale oil, high Btu gas, energy from residual carbon and other by-products with minimal environmental impact; and obtain design data and operating experience to be used for scaling up to commercial size shale retorting facilities. Preliminary design and cost data developed in this study will supplement similar information available from other engineering studies which have examined alternate retorting technologies and retorts of varying productive capacities. The new data will be beneficial to both governmental agencies and industry since it fills an information gap (i.e., demonstration-scale plant costs and technologies) not addressed by the other investigations. 19 figs., 14 tabs.